Known types of electromagnetic radiation generators can be relatively large and relatively costly not only to build but also to maintain and operate; this is especially so if commercial applications are contemplated for a radiation generator.
In the following specific reference will be made by way of example only to X-ray generators however the present invention is not limited thereto; the present invention may, for example, be applied to form an ultra violet light generator, i.e. by providing an ultra-violet light window in place of an X-ray window as described herein.
With respect to X-ray generators, synchrotrons, for example, are relatively large scale known devices which are known for use as X-ray generator devices in commercial environments. Synchrotrons have been described as possible multi-beam X-ray sources for lithography.
Discharge plasma sources have been suggested as possible candidates for a single beam point source for X-rays of relative small size and relatively low cost as compared to the multi-beam approach. Although plasma-based x-ray sources are known which are relatively small in size these have not as yet reached a level of development for commercial purposes in areas such as for example lithography. X-ray sources of this type are, for example, known which comprise an evacuatable discharge chamber an anode, a cathode, a radiation exit port and means for applying a potential as desired between the anode and cathode; see for example European patent specification publication number 0037917. Relatively, small size X-ray generators of this type are also known which exploit a hollow cathode in which the tip of an anode is axially aligned with the passage in the cathode; the presence of the hollow cathode produces beams which are more or less focused; see for example, "X-ray spots emitted in a hollow cathode ns-discharge", Plasma Sources Sci. Technol. 5 (1996) 70-77 IOP Publishing limited, printed in the UK.
It would be advantageous to have a radiation generator such as an X-ray generator which may be used in sub-micron-lithography.
It would in particular be advantageous to have a radiation source which is simple but which is able to generate short bursts of radiation having maximum intensity for nanometre wavelengths.